Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV
The review of the proton polarization experimental data on two-body deuteron photodisintegration at a photon energy between 0.2 and 2.4 GeV is presented. The NSC KIPT data are compared with the measurements of other centers and with theoretical calculations and phenomenological analysis in the frame...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Цитувати: | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV / O.G. Konovalov, S.T. Lukyanenko, P.V. Sorokin, A.A. Zybalov // Вопросы атомной науки и техники. — 2002. — № 2. — С. 9-15. — Бібліогр.: 33 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859865287271120896 |
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| author | Konovalov, O.G. Lukyanenko, S.T. Sorokin, P.V. Zybalov, A.A. |
| author_facet | Konovalov, O.G. Lukyanenko, S.T. Sorokin, P.V. Zybalov, A.A. |
| citation_txt | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV / O.G. Konovalov, S.T. Lukyanenko, P.V. Sorokin, A.A. Zybalov // Вопросы атомной науки и техники. — 2002. — № 2. — С. 9-15. — Бібліогр.: 33 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The review of the proton polarization experimental data on two-body deuteron photodisintegration at a photon energy between 0.2 and 2.4 GeV is presented. The NSC KIPT data are compared with the measurements of other centers and with theoretical calculations and phenomenological analysis in the framework of various interaction models with subnuclear (nucleons, mesons, resonances) and non-nucleon (quarks, gluons) degrees of freedom. The NSC KIPT measurements are in full accord with the data of other centers up to 0.8 GeV and confirm the dominant contribution of meson-exchange interactions and isobar configurations in the reaction γD→pn. Above 1 GeV the NSC KIPT data do not agree with the Jefferson Lab (USA) measurements which confirm the quark-gluon hypotheses about zero values of the proton polarization in this region.
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| first_indexed | 2025-12-07T15:47:46Z |
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PROTON POLARIZATION IN REACTION OF DEUTERON
PHOTODISINTEGRATION AT ENERGIES OF 0.2-2.4 GeV
O.G. Konovalov, S.T. Lukyanenko, P.V. Sorokin, A.A. Zybalov
National Science Center “Kharkov Institute of Physics and Technology”, Ukraine
e-mail: psorokin@kipt.kharkov.ua
The review of the proton polarization experimental data on two-body deuteron photodisintegration at a photon
energy between 0.2 and 2.4 GeV is presented. The NSC KIPT data are compared with the measurements of other
centers and with theoretical calculations and phenomenological analysis in the framework of various interaction
models with subnuclear (nucleons, mesons, resonances) and non-nucleon (quarks, gluons) degrees of freedom. The
NSC KIPT measurements are in full accord with the data of other centers up to 0.8 GeV and confirm the dominant
contribution of meson-exchange interactions and isobar configurations in the reaction γD→pn. Above 1 GeV the
NSC KIPT data do not agree with the Jefferson Lab (USA) measurements which confirm the quark-gluon
hypotheses about zero values of the proton polarization in this region.
PACS: 24.70.+S, 25.20.⋅X
1. INTRODUCTION
The two-body deuteron photodisintegration reaction
is a source of an information about a deuteron structure,
non-nucleon degrees of freedom, properties of virtual
nucleons in nuclei etc. The actual problem is the study
of reaction mechanisms at various photon energies, a
role of meson-nucleon and quark-gluon degrees of
freedom. For the photon energies up to 1 GeV there is a
lot of examples of the efficiency of the theory with the
nucleon, meson and isobar degrees of freedom in the
description of majority of experimental data on the
cross-sections and the polarization observables in the
reaction γD→pn. They evidence about a dominant
contribution of the meson-nucleon interaction
mechanism in this region [1]. However, there are
definite indications about possibilities of manifestation
of quark-gluon degrees of freedom in a deuteron for
NN-interactions at small relative distances (r<0.5 fm)
for this energy range too. In particular, this
manifestation is connected with a possibility of
excitation of dibaryon resonances (DR) in a deuteron at
energies of a few hundred MeV. The complexity of the
DR search in the reaction γD→pn is connected with
their absence in the explicit form in the cross-sections of
the reaction γD→pn.
For the photon energies above 1 GeV the
domination of a traditional meson-nucleon model of the
deuteron photodisintegration [3] is problematical so
long as the results of the cross-sections evaluation on
this model are not agreed with the measurements of
SLAC [4] and Jefferson Lab [5]. In these measurements
first discovered is the scaling behavior of the deuteron
photodisintegration cross-sections. The scaling mani-
festation at low-level energies is of great interest for the
theory of NN-interactions from the viewpoint of testing
the adequation of various theoretical approaches to a
structure of coupled states of two nucleons at small
distances based on the meson theory and QCD [6]. In
this connection, in investigations of the deuteron
photodisintegration reaction one of key problems is the
question about a mechanism of photon interaction with
nucleons and their excited states or structure quarks.
The search of quark-gluon effects related with a
dibaryon resonance excitation and scaling manifestation
in the cross-section measurements is complicated, on
the one hand, by a relatively small contribution of DR in
their absolute values, on the other hand, by a possibility
of scaling description with the use of meson-nucleon
model. In this connection the polarization observables
and, in particular, proton polarization can be more
sensitive to a manifestation of quark-gluon effects in the
deuteron. The estimations of 1 GeV proton polarization
with involving DR [10] lead to the considerable change
of its value in comparison with the estimates only by the
meson-nucleon model [3]. Above 1 GeV the quark
model [7] predicts zero values of the proton polarization
whereas the results obtained by the meson-baryon
model [8] give the polarization values being different
from zero significantly in the photon energy range from
1 to 1.66 GeV for the angle θр=90° cm.
All this evidences on an important role of the proton
polarization in the investigations of interaction
mechanisms in nuclei and on a necessity of their
systematical measurements in the reaction γD→pn at
intermediate energies. The Cx and Cz components of the
proton polarization in the reaction plane with using the
circularly polarized photons are of a great interest.
Besides the traditional vertical Py component of the
proton polarization measured relatively to the reaction
plane the measurements of new observable, Cx and Cz
components may be more effective for testing the
calculations of the deuteron photodisintegration reaction
by various models of interactions.
2. THE MEASUREMENTS OF THE PROTON
POLARIZATION IN THE REACTION γD→NP
The reaction of two-body deuteron photo-
disintegration, in the region above the π-meson
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2002, № 2.
Series: Nuclear Physics Investigations (40), p. 9-15. 9
photoproduction threshold (up to 2 GeV) on the nucleon
is characterized by the next pecularities of energy
behaviour of the cross-sections: the range Еγ=0.16-
0.45 GeV where ∆(1232)-isobar gives the major
contribution into the total cross-section; the range Еγ
=0.45-0.8 GeV where the channel (γN→Nπ) in the
reaction γD→pn contains Р11(1440), D13(1520),
S11(1535)-nucleon resonances; the range Еγ=0.8-2 GeV
where the channel (γN→Nπ) involves up to one and a
half ten nucleon resonances and, at the same time, for Еγ
>1 GeV is characterized by a scaling meeting the rule of
quark account [7].
The first experiment on measurements of Py proton
polarized has been carried out at the linear electron
accelerator Mark 3 (Stanford, USA) [11]. The proton
polarization is measured in the range of ∆(1232)-isobar
at Еγ=170-440 MeV and θр=40°-117° cm with using a
magnetic spectrometer, a carbon polarimeter and
scintillation counters. The proton polarization has a low
value (from −0.1 to −0.2) at photon energies from 200
to 300 MeV, however, as the energy rises its value
increases up to −0.55 for Еγ=450 MeV. In paper [12] the
results of the proton polarization measurements at the
angles θр=75° cm (Еγ=282, 342, 405 MeV) and θр=100
° cm (Еγ=358 MeV) are presented. The experiment
described in paper [12] has been carried out at the
electron synchrotron 500 MeV (Bonn, Germany) by the
method of np-coincidences using the telescope of the
scintillation counters and optical spark chambers. In
paper [13,14] the results of the proton polarization are
presented in the deuteron photodisintegration reaction in
the range Еγ=0.4-0.7 GeV. The experiment has been
carried out at the electron synchrotron INS (University
Tokyo) with using the magnetic spectrometer and
carbon polarimeter with magnetostrictive spark
chambers. The energy dependences of the proton
polarization are measured for the proton emission
angles θр=45° cm (Еγ=450-600 GeV), 70° (Еγ=400-
600 GeV), 90° (Еγ=350-700 GeV), 120° (Еγ=450-
650 GeV), 135° (Еγ=500-550 GeV). The energy
resolution was ∆Еγ∼±25 GeV. The large value of the
proton polarization (P∼0.8) first was discovered at Еγ
=500-550 MeV.
The proton polarization has been measured at NSC
KIPT at the linear electron accelerator 2 GeV in the
reaction γD→pn at Еγ=0.2-1 GeV by means of the
magnetic spectrometer and the carbon polarimeters with
optical and magnetostrictive spark chambers. The
detailed description of the procedure of measurements,
information accumulation, data processing and
obtaining the results with the error analysis is presented
in papers [15-20]. The results of these measurements are
following:
1) the systematic data of energy dependences of the
proton polarization first are obtained in the
reaction γD→pn in the range of ∆(1232) isobar (Еγ
=200-360 MeV) for the proton emission angles θ
р=25°,35°,45°,55°,65°,75° and 90° cm [15,16];
2) the proton polarization measurements are made in
the range Еγ=350-700 MeV with the energetic
resolution ∆Еγ=12.5 MeV [17,18], that is twice
better than in the measurements of [13,14]. These
results confirmed the presence of high values of
the proton polarization in the range Еγ=500-
550 MeV, though with less absolute values (P∼
0,6);
3) the proton polarization first is measured in the
reaction γD→pn at Еγ=0.75-1 GeV for the proton
emission angles θр=90° and 120° cm [19,20]. It is
necessary to mention that the measurements of the
proton polarization in this energy range are
connected with considerable background
problems at the 2 GeV linear electron accelerator
(NSC KIPT) because of the low proton yield of
the reaction under investigation and the small duty
factor of this accelerator (pulse duration ∼1 µs,
frequency 50 Hz). The presence of a large
background in the spark chambers can lead to the
appearance of a false asymmetry of a pC-
scattering which is difficult to monitor in the
experiment. It is necessary to use additional
criterions for a selection of the pC-scattering
events, for example, a back recovery of proton
tracks through the magnetic spectrometer in the
region of the deuteron target. Such a criterion is
not used in this experiment.
The first measurements of proton polarization have
been made in the reaction γD→pn at Еγ=0.5-2.5 GeV at
the electron accelerator CEBAF of Jefferson Lab [21].
The main aim of this experiment was the investigation
of the proton polarization behavior in the scaling range
of cross-sections [4,5]. The magnetic spectrometer and
the carbon polarimeter with a drift wire chamber was
used for these measurements. Using of the continuous
electron beam from the accelerator CEBAF essentially
decreases a level of a background in the track detectors.
The large electron current of the accelerator provides
the effective collection of the pC-scattering events even
for the reaction with small cross-sections. Besides, to
exclude a background contribution into the proton
polarization, we used the procedure of the back
recovery of the proton track from the polarimeter
through the magnetic spectrometer into a deuteron
target region. The Cx and Cz components of proton
polarization first were measured in the reaction at a
photon energy of 0.5-2.5 GeV.
The data of experimental investigations of Py proton
polarization in the reaction γD→pn at Еγ=0.2-0.7 GeV
are presented in Fig. 1 and 2 [11-18,21]. The results of
measurements [11-14] are agreed with the most full
NSC KIPT data [15-18] in this region. The polarization
data for angle 90° cm are presented in Fig. 3 in a more
wide photon energy interval (Еγ=0.5-2.5 GeV)
[11,13,15,16,17,19,20,21]. The NSC KIPT data are not
agreed with the measurements at Jefferson Lab (USA)
in the interval Еγ=0.75-1 GeV. As was mentioned above
a possible cause of such disagreement is a false
asymmetry of pC scattering created by the large
background in the spark chambers of the polarimeter at
the exit of the 2 GeV linear electron accelerator (NSC
KIPT). The results of proton polarization measurements
allow one to hold the effective examination of
calculations of the reaction γD→pn with the use of
10
various mechanisms of interactions from the
photomeson threshold to 2.5 GeV.
-0.5
-0.3
-0.1
0.0
0.1
0.2
200 300 400 500 600 700
Θ
cm
=250
P Eγ , MeV
-0.5
-0.3
-0.1
0.0
0.1
0.2
100 200 300 400 500 600 700
Θ
cm
=250
P Eγ , MeV
-0.6
-0.4
-0.2
0.0
0.1 200 300 400 500 600 700
Θ
cm
=350
-0.6
-0.4
-0.2
0.0
0.1 200 300 400 500 600 700
Θ cm=350
-0.6
-0.4
-0.2
0.0
0.2
200 300 400 500 700
Θ
cm
=450
-0.6
-0.4
-0.2
0.0
0.2
200 300 400 500 700
Θ cm=450
-0.8
-0.6
-0.4
-0.2
0.0
200 300 400 500 600 700
Θ
cm
=700
-0.8
-0.6
-0.4
-0.2
0.0
200 300 400 500 600 700
Θ
cm
=700
-0.6
-0.4
-0.2
0.0
200 300 400 500 600 700
Θ
cm
=550
-0.6
-0.4
-0.2
0.0
200 300 400 500 600 700
Θ cm=550
Fig. 1. Energy dependences of the proton polarization in the γD→np reaction for the proton angles θcm=25°,35°
,45°,55°,70°. The open circles − Kharkov [15,16,18]; the solid circles − Stanford [11]; the solid triangles − Tokyo
[14]; the dash curves − J. Laget [3]; the dash-dotted curves − K. Ogawa [22]; the dotted curves − H. Ikeda [14];
the dash-double dotted curves − V.P. Barannik, V.B. Ganenko [16,28]; the solid curves − V. Leidemann [32]
3. COMPARISON WITH THE
THEORETICAL ESTIMATIONS OF THE
REACTION γD→NP
Above the photomeson threshold on the nucleon, the
first theoretical study of the two-body deuteron
photodisintegration with the calculations of the proton
polarization was made by Laget [3]. He first used a
diagrammatical approach for the description of the
reaction γD→pn. The calculation was performed in the
no relativistic model with using the pole nucleon and
deuteron diagrams, meson-exchange diagram with
excitation of ∆-isobar in the intermediate state and the
final-state interactions between the two nucleons (FSI).
The results of the total cross-section calculations by this
model are agreed adequately with the experiment up to
Еγ=500 MeV. The angular dependences of the cross-
section dσ/dΩ agrees with the experimental data for the
photon energy 0.2-0.4 GeV only for the angles around
90° cm. The calculations of the Σ-asymmetry of cross-
sections for the linearly polarized photons agree with
the experiments at the energies Еγ=0.2-0.4 GeV.
11
-0.8
-0.6
-0.4
-0.2
0.0
0.1 300 500 700
Θ
cm
=780
P Eγ , MeV
-0.8
-0.6
-0.4
-0.2
0.0
0.1 300 500 700
Θ cm=780
P Eγ , MeV
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
300 500 700
Θ
cm
=900
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
300 500 700
Θ
cm
=900
-0.8
-0.6
-0.4
-0.2
0.0
0.2
300 500 700
Θ
cm
=1200
-0.8
-0.6
-0.4
-0.2
0.0
0.2
300 500 700
Θ
cm
=1200
Fig. 2. Energy dependences of the proton polarization in the γD→np reaction for the proton angles θcm=78°,90°
,120°. The open circles − Kharkov [15,16,17,18]; the solid circles − Stanford [11]; the solid triangles − Tokyo
[13,14]; the open squares − Bonn [12]; the solid squares − Jefferson Lab [21]. The curves have the same as in
Fig. 1
The estimations of the proton polarization by the
Laget's model [3] are presented in Figs. 1 and 2. The
Laget's results coincide with the measurements of
proton polarization only for the angles θр<55° cm in the
region of ∆(1232)-isobar. However, for θр>55° cm
significant disagreements between the model results and
the measurements were observed.
In the framework of a covariant approach Ogawa
et al [22] have calculated the amplitude of the deuteron
photodisintegration with including the pole nucleon and
deuteron diagrams and the diagram with an excitation of
the ∆(1232)-isobar and nucleon resonance P11(1440). In
this model various simplifying assumptions are made in
contrast to the Laget's model. For example, the
following items are disregarded: the deuteron D-state
wave function in the calculation of the one-pion
reabsorbtion diagram; the contribution of the two-pion
exchange diagram; the final-state interaction between
the two nucleons; the Fermi motion of the nucleons in
the deuteron. The results of the cross-section
calculations agree with the measurements up to the
photomeson threshold. However, for Еγ>300 MeV, it is
clearly necessary to take into account nucleon
resonances higher than the P33. A problem here is that it
is almost prohibitive to make covariant calculations for
higher resonances, since their vertex function is not well
know. In this model the virtual process γN→N∗→Nπ
was presented by the phenomenological helical single-
pion photoproduction amplitudes given by Moorhouse
et al [23]. Such a procedure gave the possibility to
improve essentially the description of the cross-section
in this region. Besides the cross-section, the proton
polarization was calculated in this model. These results
are presented in Figs. 1 and 2. The agreement of the
theoretical values of proton polarization with the
experiments only for θр<55° cm and Еγ=200-300 MeV
is observed. To improve the agreement with the
experiments, the dibaryon resonances were introduced
12
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
300 600 900 1200 1500 1800 2100 2400
P
Eγ , MeV
Θ
cm
=900
Fig. 3. Energy dependences of the proton polarization in the γD→np reaction for the proton angles θcm=90°.
The open circles − Kharkov [15,16,17,19,20]; the solid circles − Stanford [11]; the solid triangles − Tokyo [13];
the solid squares − Jefferson Lab [21]. The solid curve − Y. Kang [8]
in the analysis [22]. To explain the polarization data the
partial-wave analysis with including the dibaryon
resonances in the deuteron photodisintegration [13,14]
was made. The basic assumptions adopted in this
analysis are as follows:
1) the γD→pn amplitudes consist of the non-resonant
part and resonant part;
2) the non-resonant amplitudes are calculated and
consist of the nucleon-exchange Born term and
one-pion reabsorption term;
3) the one-pion reabsorption term based on the
model Ogawa et al is calculated [22];
4) the resonant amplitudes are due to the s-channel
formation of dibaryon resonances.
The resonant amplitudes are taken into account
through E, H-multipole expression and are parametrized
by Breit-Wigner form, where the masses W0, widths Г
and coupling parameters were determined from χ2-
minimization fits to the experimental data. The criteria
for acceptable fits are:
1) χ2/df (degrees of freedom)<2;
2) Г<350 MeV;
3) 2200 MeV<W0<2480 MeV.
In conformity with these criteria the best fit to the
experimental data of the cross-section and the proton
polarization was ensured in the interval Еγ=0.2-0.7 GeV
by DR with I(JP)=1(3−) (W0=2300 MeV, Г=213 МeV),
0(1+) (W0=2350 МeV, Г=342 МeV) and 0(3+)
(W0=2380 МeV, Г=215 МeV) in the combinations 1(3−)
+0(1+) and 1(3−)+0(3+) with the non-resonant part of the
amplitude of the reaction. The results of the fits to
experimantal data are following:
1) the including of DR with quantum numbers
I(JP)=1(3−), 0(1+) and 0(3−) improved essentially
the description of the differential cross-sections in
the region Еγ=0.4-0.7 GeV for the angles θр=90
° cm in comparison with the non-resonant model
[22];
2) the results of the partial-wave analysis [13,14]
with the consideration of three DR agree with the
measurements of the proton polarization in the
reaction γD→pn in the energy range from 0.4 to
0.7 GeV and at angles θр=45°-135° cm, i. e. in the
region of its maximum values (Fig. 1 and 2);
3) the prediction for the partial-wave analysis [14]
with the given set of DR does not describe the
angular distributions of the experimental data on
the Σ-asymmetry of cross-sections with linearly
polarized photons for energies between 0.25 and
0.6 GeV [24];
4) the prediction for the polarized target asymmetry
is in bad conformity with the experimental data.
Although the results of analysis [14] agree badly
with the experimental data of Σ and T-asymmetries, the
success of the description of the proton polarization in
the region 0.4-0.7 GeV with using DR became a definite
confirmation of a mechanism related to with a
manifestation of quark degrees of freedom in the
deuteron [26,27]. This result promoted a further
development of partial-wave analysis of the
experimental data in the reaction γD→pn with an aim to
examine the efficiency of the DR model for description
of a more wide set of polarization observables.
In the papers [16,28] offered the results of multipole
analysis (NSC KIPT) of the reaction γD→pn in the
region Еγ=0.2-0.6 GeV with using dσ/dΩ, Σ, T and Р
experimental data. This analysis was made in the
framework of the gauge-invariant pole model
considering the γN→Nπ amplitudes and the deuteron
structure without DR and with different sets of isovector
and isoscalar DR knowing from papers [29,30,31]. In
total this analysis included nine DR with quantum
numbers I(JP)=1(2+) (W0=2150 МeV, Г=106 МeV), 1(3
−) (W0=2260 МeV, Г=154 МeV), 1(0+) (W0=2050 МeV,
Г=195 МeV), 1(1−) (W0=2179 МeV, Г=87 МeV), 1(4+)
(W0=2470 МeV, Г=150 МeV), 0(1+) (W0=2140 МeV,
Г=342 МeV), 0(3+) (W0=2362 МeV, Г=238 МeV), 0(3
−) (W0=2230 МeV, Г=150 МeV). DR amplitudes are
parametrized in the Breit-Wigner form but with the
fixed values of the mass W0 and width Г unlike [13,14].
Residues ml, phase factor exp(iϕDR) and barrier
parameter X are used as parameters of fits to the
13
experimental data. In these fits to dσ/dΩ, Σ, T, P data
various sets of DR and without DR were included with
the use of pole and N∆-diagrams only starting from a
minimization of χ2/df. The minimum value of χ
2/df=1.74 was got with including all the nine DR. The
results of the given partial-wave analysis of the reaction
γD→pn in the region Еγ=0.2-0.6 GeV are as follows:
1) the satisfactory description of angular
distributions of the cross-sections, in particulary,
in the region θр<60° cm, where the results of the
analysis [14] do not agree with the experiment has
been obtained;
2) the results of analysis [28] entirely repeat the Σ-
asymmetry cross-section angular distribution with
linearly polarized photons in the interval Еγ=0.18-
0.4 GeV and partly at energies 0.5-0.6 GeV [24];
3) in the framework of the given analysis the
satisfactory description of the proton polarization
in the region between 0.35 and 0.6 GeV for the
angles θр>45° is achieved, however, for θр<45°
the agreement is not observed (Fig. 1 and 2);
4) the results of analysis [28] agree mainly with the
measurements of a polarized target T-asymmetry
[25].
As a whole the addition of the meson-baryon model
by diagrams with the DR excitation in the intermediate
state is a rather effective means for the description of
the experimental data in the reaction of the deuteron
photodisintegration in the photon energy range from 0.3
to 0.7 GeV and at proton emission angles θр=45°-135
° cm. However, in the meson-baryon model which were
used in the analysis [13,14,16,28] one did not
considered the whole set of possible effects which can
influence on the description of the experimental data.
These effects are following: FSI, meson-exchange
currents, various isobar configurations in the
intermediate state, the consideration of more high
resonances, relativistic effects, the features of deuteron
wave function behaviour at small distances etc. It is
necessary to study in detail all these and other possible
effects in the framework of meson-baryon model, their
contributions in the cross-section and the polarization
observables to convince in the necessity of including
DR for the description of the reaction.
This is evidenced by the results of the dσ/dΩ, Σ and
Р estimation in the γD→pn at the energies Еγ=0.16-
0.5 GeV [32] where the DR contribution is not
considered but the contribution meson-exchange
currents, various N∆ and ∆∆-isobar configurations and
FSI are analyzed in detail. The final-state interactions
are considered in the approach of the (NN, N∆, ∆∆)-
coupling channels in the states (2S+1LJ) with J≤3 for
every channel. The results of the calculations of the Σ-
asymmetry and the cross-sections agree adequately with
the experiments. The proton polarization calculations
are shown in Fig. 1 and 2. We should note the
significant improvement of the description of the proton
polarization measurements by this model in comparison
with MBM from papers [3,13,14,16,22,28], though the
difference in the region of maximal values of the proton
polarization is remained. The including of D13(1520)
and S11(1535)-nucleon resonances did not lead to a
significant improvement of the proton polarization
description.
The calculation of the deuteron photodisintegration
has been carried out in the range from the photomeson
threshold to 1.6 GeV on the base of the meson-baryon
model [8]. This estimate includes π, ρ, η and ω-
exchanges, plus all good established nucleon and ∆-
resonances with a mass less than 2 GeV and J≤5/2. The
calculation suggests that final-state interaction effects
are insignificant and that the Born amplitudes are nearly
real. The results of the proton polarization calculation
together with the experimental data are presented in
Fig. 3 for the angle θр=90° cm. The calculated proton
polarization has the maximum value P~0,5 in the photon
energy range 0.25-0.7 GeV and are enough near to the
results of partial-wave analysis with including DR
[13,14,16,28]. This result evidences about the necessity
of further theoretical investigations of the reaction γD→
pn in the framework of MBM in the given region.
In the range Еγ=0.7-1.6 GeV the maximum values of
the proton polarization [8] are close to the NSC KIPT
measurements [19,20] and are do not agree with the
Jefferson Lab measurements [21]. The zero values of
the proton polarization [21] confirm the quark
mechanism of the photon absorption in the deuteron [7]
in the scaling region of the cross-sections, although such
results for the cross-sections are obtained in the
framework of the asymptotic meson-exchange model
[8,9]. The results of the measurements of the Cx and Cz
components of the proton polarization [21] do not agree
with the prediction of the quark model [7].
The results of the systematic polarization
investigations of the deuteron photodisintegration up to
1 GeV evidence about a dominant contribution of the
meson-baryon mechanism of interactions although in
the theory of this process there is not united concept
about contributions of FSI, nucleon resonances, various
meson-exchange mechanisms et al. In these conditions
the DR role remains for now problematic. First of all it
is necessary to improve the precision of the theoretical
and experimental investigations of the deuteron
photodisintegration to have a possibility to distinguish
even the small contributions of these resonances. In the
range Еγ=1-4 GeV the systematic polarization
investigations practically are only at the start but the
study of a role of meson-baryon and quark mechanisms
of interactions at the level of cross-sections does not
give still an unambiguous answer in favour of one or
another mechanism.
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16
PACS: 24.70.+s, 25.20.x
|
| id | nasplib_isofts_kiev_ua-123456789-80103 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T15:47:46Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Konovalov, O.G. Lukyanenko, S.T. Sorokin, P.V. Zybalov, A.A. 2015-04-11T19:11:35Z 2015-04-11T19:11:35Z 2002 Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV / O.G. Konovalov, S.T. Lukyanenko, P.V. Sorokin, A.A. Zybalov // Вопросы атомной науки и техники. — 2002. — № 2. — С. 9-15. — Бібліогр.: 33 назв. — англ. 1562-6016 PACS: 24.70.+S, 25.20.⋅X https://nasplib.isofts.kiev.ua/handle/123456789/80103 The review of the proton polarization experimental data on two-body deuteron photodisintegration at a photon energy between 0.2 and 2.4 GeV is presented. The NSC KIPT data are compared with the measurements of other centers and with theoretical calculations and phenomenological analysis in the framework of various interaction models with subnuclear (nucleons, mesons, resonances) and non-nucleon (quarks, gluons) degrees of freedom. The NSC KIPT measurements are in full accord with the data of other centers up to 0.8 GeV and confirm the dominant contribution of meson-exchange interactions and isobar configurations in the reaction γD→pn. Above 1 GeV the NSC KIPT data do not agree with the Jefferson Lab (USA) measurements which confirm the quark-gluon hypotheses about zero values of the proton polarization in this region. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Nuclear reactions Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV Поляризация протонов в реакции фоторасщепления дейтрона в интервале энергий фотонов 0.2-2.4 ГэВ Article published earlier |
| spellingShingle | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV Konovalov, O.G. Lukyanenko, S.T. Sorokin, P.V. Zybalov, A.A. Nuclear reactions |
| title | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV |
| title_alt | Поляризация протонов в реакции фоторасщепления дейтрона в интервале энергий фотонов 0.2-2.4 ГэВ |
| title_full | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV |
| title_fullStr | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV |
| title_full_unstemmed | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV |
| title_short | Proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 GeV |
| title_sort | proton polarization in reaction of deuteron photodisintegration at energies of 0.2-2.4 gev |
| topic | Nuclear reactions |
| topic_facet | Nuclear reactions |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/80103 |
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